104 



DIPTERA OF MINNESOTA. 



There are at this writing only about 78 known North American 

 species in the entire group. The family is especially interesting on 

 account of the peculiar habits of the larvae of some of the species, 

 regarding which there is much to be learned. These larvae live 

 parasitically in the interior of wasps, bees and locusts. One observer 

 claims that he has seen the adult flies follow bumble bees and alight 

 upon them for the purpose of oviposition, and it is supposed that the 

 larva, upon hatching, bores its way into the body of the bee. Some 

 naturalists have believed that it is in the nests of the bees and upon 

 the larvje and pupae that the eggs are laid. This theory, however, 

 is hardly to be entertained, since they have never been reared from the 

 larvae or pupae, though frequently bred from the imago. Members 

 of the genus Conops have emerged from the body of a bumble bee 

 several months after the death of the latter. The larvae of those which 

 infest bees are large, one, when full grown, occupying almost all of 

 the space in the abdomen of the bee parasitized. 



Fig. 101. A Thick-headed Fly, Physocephala tibialis, not taken in Minnesota. Lugger. 



We have taken in this state : Myopa clausa, Loew., Fig. 5, Plate 

 II ; M. vesiculosa, Say. ; M. pilosa, Will. ; Physocephala affinis. Will. 

 P. furcillata, Will. ; P. marzinata, Say ; Oncomyia abbreviata, Loew. 



